In European Patent Application 0317357 which corresponds to U.S. Pat. No. 4,958,874, there is disclosed a mobile unit comprising a lorry trailer having an elongate floor, an elongate roof and two generally parallel and elongate side-walls comprising panels which are pivotable relative to the trailer base so as to provide an expanded unit with a larger area than the elongate floor, the trailer also having side-roof portions which unfold therefrom to cover the areas of the expanded unit at each side of the elongate roof, the side-roof portions being mounted on upwardly slidable structural members. Such a unit is suitable for a range of vehicle bodies, but for certain vehicles the necessary cost of modification of the structure becomes prohibitively expensive. In particular the weight of the sliding arrangement necessitates strong support columns extending from the floor of the vehicle.
Expandable trailers are also known from U.S. Pat. No. 3534997 and from PCT Application WO 81/00989. In the former, the expanded floor area pivots downwardly from the side of the vehicle and then the expanded roof portion pivots out from the top of the vehicle. In the latter, the floor again pivots down from the side of the vehicle but the roof is then deployed upwardly from the horizontal floor.